# [tex4ht] another problem with mathjax mode: Forbidden control sequence found while scanning use of \AltlDisplay

Nasser M. Abbasi nma at 12000.org
Tue Jan 22 03:41:04 CET 2019

This problem I've seen before. But now I have this large latex file
that I am trying to compile, which has 1000's of such constructs
as follows.

A tabular which contains math entries like this in a cell:

$\left[ \begin{array}{cc} 0 & 1 \\ -25 & -4 \end{array} \right]$

latex has no problem with these, nor svg or png. But mathjax
does not like it. Here is MWE

===================================
\documentclass[11pt]{article}
\usepackage{amsmath}
\begin{document}

\begin{tabular}[c]{|p{2in}|p{2in}|}
test
&
$\left[ \begin{array}{cc} 0 & 1 \\ -25 & -4 \end{array} \right]$
\end{tabular}
\end{document}
======================================

make4ht -ulm draft foo.tex "htm,mathjax"
gives

(/usr/local/texlive/2018/texmf-dist/tex/generic/tex4ht/html5.4ht)) (./foo.aux)
(/usr/local/texlive/2018/texmf-dist/tex/latex/lm/ot1lmtt.fd)
Runaway argument?
\left [\begin {array}{cc} 0 \@endpbox \hskip \tabcolsep \hskip -.5\arrayrulewi
dth \ETC.
! Forbidden control sequence found while scanning use of \AltlDisplay.
<inserted text>
\par
l.12                           0      &
1  \\
? C

The fix is to add { and } inside the math, like this

================
\documentclass[11pt]{article}
\usepackage{amsmath}
\begin{document}
\begin{tabular}[c]{|p{2in}|p{2in}|}
test
&
$\left[ {\begin{array}{cc} 0 & 1 \\ -25 & -4 \end{array} } \right]$
\end{tabular}
\end{document}
==============================

Notice the "{" added before \begin{array} and at end.

But it is not possible for me to edit manually this large
file and add {} everywhere, as there are thousands of such places.

I'll try global search and replace and hopefully not break anything else.

But is there a reason why this problem keeps hapenning with mathjax
and no other system?  Is this a mathjax issue itself
or the translation to mathjax done by tex4ht?

Thank you
--Nasser
TL 2018